This invention relates generally to a method of programming, with at least a series of time intervals and a series of sample rates, a means for recording at least one detected phenomenon occurring during a series of events. More particularly, but not by way of limitation, the present invention relates to a method of recording in an electronic memory device pressure and temperature detected during a plurality of events which occur in a well.
It is, of course, known that there is a need for methods for recording phenomena during various events. For example, pressure and temperature in a downhole environment often need to be recorded during alternately flowing and non-flowing (closed-in) periods during the testing of an oil or gas well.
In the specific example of the testing of an oil or gas well, it is known that a Bourdon tube device can be used to mechanically record pressure and temperature by creating a scribed metallic chart containing a line representing the detected phenomenon, such as pressure. The Bourdon tube device has at least two shortcomings in that it has a limited data recording capacity and a limited programability.
As an alternative to the Bourdon tube type of recording device, electronic memory gauges have been used to electronically record pressure and temperature in electrical digital form. In the specific example of data recordation during the testing of an oil or gas well, various electronic memory gauges have been manufactured or marketed by such companies as Geophysical Research Corporation, Sperry Corporation, and Panex Corporation. These devices have used electronic memories for receiving digital data derived from transducers which are responsive to pressure or temperature.
The types of such electronic memory gauges known to us have a shortcoming in that they can only be programmed to sample pressure and temperature, for example, at one set of contiguous time intervals. Although the interval lengths can be varied within predetermined ranges, only one set of time intervals can be programmed into the electronic memory gauges at one time. Heretofore, this one set of time intervals has corresponded to a single set of time period at which the events have been anticipated to likely occur. For example, if it were desired to record pressure and temperature in a well during two different events, such as a flowing period and a closed-in period, one such electronic memory gauge would be programmed with a first estimated time interval during which it was anticipated that the flowing event would occur and with a second estimated time interval during which it was anticipated that the closed-in event would occur. Because the pressure and temperature are generally to be recorded at different rates during different events, one sample rate would be entered for the first time interval and another sample rate would be entered for the second time interval. This presents a problem in that if the actual times of the flowing and closed-in events are not correctly estimated by the selected time intervals, the rates at which the pressure and temperature will be sampled during the respective time intervals will not correctly correspond to the desired sample rate for the event that is actually occurring.
By way of a more specific example, assume that it will take six hours to run a testing string containing the memory gauge into the well borehole. During this event of running into the hole, the sample rate for recording the phenomena (e.g., the pressure and temperature) is to be 10 minutes. Assume that the next event is a first flow period which is to be completed within 30 minutes following the running of the testing string into the hole. During this interval, the sample rate is to be 3 minutes. Subsequent events, with their estimated time of completion and their desired sample rates shown in parentheses, include a first closed-in period (1 hour, with a sample rate of 15 seconds), a second flow period (1 hour, with a 3 minute sample rate), a second closed-in period (2 hours, with a 15 second sample rate for the first hour and a 1 minute sample rate for the second hour), and pulling out of the hole (6 hours, with a 10 minute sample rate). If any of the foregoing anticipated time schedules, which have been entered into the memory gauge as known to the art, is not precisely met by what actually occurs (as is the case in nearly every well test), it can be readily understood from the foregoing that such a difference between the actual and estimated times for the events will most likely cause the detected phenomena during subsequent events to be sampled at a rate which is different from the desired rate for the specific event. For example, if it actually took 7 hours to run into the hole, rather than the estimated 6 hours with which the aforementioned gauge was programmed, the memory gauge would be taking 15-second samples during the actual first flow event rather than the desired 3-minute samples. Assuming the actual first flow event lasted the estimated 30 minutes, then during the subsequent actual first closed-in period the gauge would be taking samples at the 3-minute sample rate which was programmed to commence at 7.5 hours from the starting time. During the actual first closed-in period, the gauge would not be gathering the quantity of information that was desired.
Therefore, there is the need for a method by which a recording means, such as an electronic memory gauge used for recording pressure and temperature in an oil or gas well, can be programmed to record the detected phenomena so that the desired quantity of data is less likely to be lost due to a difference between the estimated time at which an event is anticipated to occur and the actual time at which the event occurs. It is also desirable that such a new method be capable of use with a specific presently known memory device which can ultimately receive only a single set of time intervals. There is also the need for such a method to be capable of selecting a sample rate and a sample ratio for each time interval.